Dust produced during the manufacturing, handling, transport, storage, crushing, and utilization of fining particulate-producing materials is a common problem for several industries.
Inorganic substances, such as salts of phosphates, nitrates, chlorides, sulfates, etc., are widely used as fertilizers in the agricultural area. Methods of manufacturing or processing these inorganic compounds into particles are also known. Regardless of method or nature of the compound, the resulting particulate materials can easily break into smaller particles (10 micron or smaller), often resulting in an undesirable level of particles fine enough to become airborne dust, particularly when handled, stored or transported.
Fertilizer dust dissemination poses safety, health, environmental, housekeeping and maintenance problems for the producers, distributors and consumers. For instance fertilizer dust has raised health concerns due to human and animal inhalation thereof. It is also a concern when fertilizer dust becomes airborne what can lead to the loss of agronomic and economic value, while potentially contributing to the contamination of surface water ecosystems.
Depending upon the type of substrate, simple remediation like aspiration and water spray may be applied. Otherwise, the vast majority of commercially produced fertilizers are treated with an additive agent to reduce dust formation levels.
Besides the considerable amount of prior art references directly or indirectly related to anti-dust agents in the fertilizer industry, the majority refers to the use of complex synthesis compounds with a binder function, such as some quaternary compounds, or petroleum-based products.
Until this time, treatment of inorganic particulates, such as fertilizers, has focused on petroleum-based products, mineral oils, and waxes. To reduce the dust on fertilizer, a petroleum residue or hydrogenated mineral oil is typically sprayed onto the fertilizer in order to act as an anti-dusting agent. The application of the anti-dusting agent occurs generally during the drying step of the phosphate granules. This facilitates the complete coverage of the coating onto the fertilizer particle surface.
However, there are disadvantages in such treatment methods. With time, oils tend to volatilize and/or soak into the fertilizer and lose their effectiveness, while waxes and petroleum-based products are difficult to handle, and can require special heating equipment. Inorganic particulates coated with petroleum-based products can generate residues on handling equipment, and, in the case of coated fertilizers, typically result in the separation of scum upon dissolution of the fertilizer in water. In addition, such additives do not provide biodegradable coatings.
The application of by-products from organic industries was little investigated to that end. For instance, some by-products derived from the paper making industry, such as lignosulfonate, or glycerin-containing by-products derived from the transesterification industry have already been proposed as dust controlling agents.
In this sense, urea and other fertilizers have been treated with lignosulfonates alone, or in combination with a co-additive, such as molasses. U.S. Pat. No. 5,328,497, filed by Georgia-Pacific Corp (1994) teaches preventing dusting and caking of fertilizer by using an aqueous solution containing lignosulphonate, sugar and urea. However, because aqueous solutions of urea and lignosulfonate have low volatility, they lose their effectiveness long after application.
Other proposed dust control methods for specific fertilizers include application of mixture solutions containing carbohydrates, molasses, gypsum, saccharides, starch, glycerin, polyethylene glycol, triethanolamine and even water. For instance, U.S. Pat. No.7,816,561, filed by Yara International ASA (2008), discloses a method for improving the crushing strength and reducing the dust formation and the caking tendency of urea particles by using carbohydrates. JP56084315, filed by Mitsubishi Chem Ind (published in 1981), teaches a granulated fertilizer consisting of a mixture of gypsum powder and molasses, wherein the gypsum can be used suitably as a land improver, a component of bulk blend fertilizer, etc. JP1270583, filed by Lida Kogyosho KK (1989) refers to a granulated fertilizer formed from fine magnesium silicate powders mixed with an aqueous solution of a binder such as molasses. EP401550, filed by Kali Und Salz AG (1993), teaches the inhibition of dusting in pellets or granules using a solution of molasses and concentrated alkaline earth metal chloride solution. FR2723085, filed by Meac SA (1996), describes a fertilizer product combining a mineral support with anti-dust additives, such as mineral or vegetal oils, molasses, amines and/or water. JP2001158685, filed by Oji Cornstarch KK (2001), teaches a granulated fertilizer consisting of iron and steel slag, and a binder comprising saccharides and a starch powder.
U.S. Pat. No. 3353949, filed by Cyanamid Co. (1967), teaches that a granular fertilizer is treated with a liquid conditioner additive selected form water-soluble sugars, such as glucose, dextrose and black strap molasses, which permits ready occlusion of nutrients. U.S. Pat. No. 5,383,952, filed by Kali & Salz AG (1995), discloses a process for preventing dusting in fertilizer granules during the loading or transporting of granulates, comprising: adding to said granulates a dust-binding, liquid mixture consisting of molasses and another liquid selected from the group consisting of glycerin, polyethylene glycol, triethanolamine and the mixtures thereof. While liquid treatment compositions, such as these, may reduce the fertilizer dust levels, the liquid compositions coated on the fertilizer particles tend to promote caking of the granular fertilizer particles, another inconvenience to be avoided.
For specific organomineral fertilizer manufactured from fire extinguishing powder waste, binding materials derived from distillery industry were also proposed (CZ11701, filed by Jaroslav et al. (2002) and WO06056602, filed by Valoragri SA (2006)).
Numerous attempts to reduce dustiness of inorganic fertilizers, however, through improvements in the fertilizer manufacturing process, have been largely unsuccessful. These methods have a number of disadvantages as well. Aqueous solutions and emulsions tend to accelerate the formation of fertilizer dust and exacerbate the fertilizer particles caking tendencies.
While these conditioning agents provided an improvement in dust control over oils, waxes, and oil/wax blends, they do not provide the degree of binding required for effective long-term dust control. Other liquids also have been used for fertilizer dust control including lignosulfonate solutions, amines, surfactants, waxes, wax emulsions and water alone, but have not proved completely satisfactory.
One prevalent problem is that the use of aqueous treatment solutions tends to exacerbate the caking problem often encountered with inorganic fertilizers. The use of other by-products did not solve the problem completely, as it generally refers to the use of by-products derived from sugar cane or sugar beet industries, such as vinasses or molasses, with uncontrolled amount of sugar, whose content and quality depend on the particular method of extraction, maturity of the sugar cane or sugar beet, the amount of sugar extracted, and the method of extraction or specifically adapted for only one type of fertilizer.
Similarly, dust produced during the handling, transport, storage, crushing, and utilization of coal, petroleum coke, minerals or products from mining industry in general, is not only a nuisance, it is a major health and safety issue. Fires, explosions, and black lung cost the petroleum, mining, utility and steel industries millions of dollars annually due to lost production, medical expenses, lost equipment, and high insurance premiums.
In addition to dust generation, erosion and loss of substrate is another common problem found on surfaces that are prone to particulate generation, particularly those subject to vehicular, pedestrian or other sorts of traffic.
Dust from mining industry is produced and airborne by two major mechanisms: impact or wind erosion.
The impact can produce a substantial amount of airborne particulate matter. Fine particulates also are produced during stacking, crushing, milling, breaking, or reclaiming operations.
One method that has been used to control such dust is by spraying the mining product with water. Water is effective to prevent dusting; however, it evaporates quickly. Therefore, the mining product must be sprayed almost continuously in order to be an effective anti-dusting agent. This continuous spraying is cumbersome and costly, and the droplets of water in the spray often do not even capture the finest, most hazardous particulates. Furthermore, not all mining product can be wetted using water, and, in some uses, moisture level restrictions will be exceeded if too much water is used. Also, an economic penalty may result because it is less efficient to burn high moisture mining product. Surfactants or hydroscopic salts such as magnesium chloride or calcium chloride can be added to the water to improve wettability in some instances; however, the problem of evaporation remains.
Another method used to control dust generation is spraying the area with an oil based composition. Although quite effective at suppressing dust generation for extended periods of time, this method is not environmentally sensitive. In addition to the harm it can impose on the environment, it may pose a significant long term clean-up problem and even potential health hazards. Moreover, the oil treated substrates may adhere to vehicles attempting to travel over the treated substrate, generating unwanted clean-up, excess wear on mechanical equipment, and accelerated breakdown of the treated surface.
The prior art also teaches some compositions consisting of mixture solutions containing molasses, sugars or by-products thereof, but have not proved completely satisfactory. For instance, U.S. Pat. No. 4,582,511, filed by Shell Oil Company (1986), U.S. Pat. Nos. 5,536,429 or 6,790,245, filed by Benetech, Inc. (1996 or 2004), WO 04073928, filed by Archer-Daniels-Midland Company (2004), EP 2228420, filed by Japan Corn Starch Co., LTD. (2010).
Thus, there remains a need in the art for a biodegradable anti-dusting agent which effectively reduces the level of dust emission from inorganic fertilizers or mining industry and that can be used for a large range of inorganic fertilizers, or mining products in general.